/Engine/Source/Runtime/Engine/Classes/Materials/MaterialInstance.h
Overrides the default value of the given parameter (transient). This is used to implement realtime previewing of parameter defaults. Handles updating dependent MI's and cached uniform expressions.
virtual void OverrideNumericParameterDefault ( EMaterialParameterType Type, const FHashedMaterialParameterInfo & ParameterInfo, const [UE::Shader::FValue](API\Runtime\Engine\Shader\FValue) & Value, bool bOverride, [ERHIFeatureLevel::Type](API\Runtime\RHI\ERHIFeatureLevel__Type) FeatureLevel )